Electric valve circuit



May 28, 1940. B. D. BEDFORD ET AL 2,202,728

ELECTRIC VALVE CIRCUIT Filed Oct. 26, 1939 Their Attorney.

Patented May 28, 1940 UNITED STATES PATENT OFFICE Meyer, Scotia, N. Y.,

Electric Company, a

assignors to General corporation of New York Application October 26, 1939, Serial No. 301,394

6 Claims.

Our invention relates to electric valve circuits and more particularly to control or excitation circuits for electric valve means of the type employing ionizable mediums such as gases or vapors.

Electric valve apparatus of the type employing an ionizable medium and comprising a control member of the make-alive or immersion-ignitor type has been rather generally applied in commercial translating apparatus. These control members are of a material such as boron-carbide or silicon-carbide and have an extremity thereof in contact with an associated cathode which may be a liquid or a solid. In one form of the electric valve commonly employed, the cathode is a pool of mercury and one extremity of the control member extends into the mercury. One form of control circuit for this type of electric valve means comprises means responsive to the polarity of the applied anode-cathode voltage. This type of excitation circuit has many advantages, one of which is the relatively small requirements as to auxiliary control equipment since the control or excitation circuit may be energized from the main transformer which energizes the anode-cathode circuit of the electric valve. In accordance with the teachings of our invention described hereinafter, we provide a new and improved excitation circuit which obviates several of the difliculties experienced heretofore in the general application of this type of control or excitation system.

It is an object of our invention to provide a new and improved electric valve circuit.

It is another object of our invention to provide new and improved control or excitation systems for electric valve apparatus of the type employing immersion-ignitor control members.

It is a further object of our invention to provide a new and improved control circuit for electric valve apparatus in which the control circuit is energized in response to the polarity of the applied anode-cathode voltage and in which the control circuit is immediately deenergized upon initiation of an arc discharge within the principal electric valve means.

Briefly stated, in the illustrated embodiments of our invention we provide new and improved excitation circuits for electric valve means of the type employing immersion-ignitor control members and in which the excitation circuits may be energized from extensions of the main transformer windings which energize the anode-cathode circuits of the electric valve means. Suitable means, such as saturable inductive devices, are connected in the anode-cathode circuits of the main valves and the associated control valves to render the control valves non-conductive and thereby to efiect deenergization of the immersion-ignitor control members upon initiation of arc discharges within the main valves.

For a better understanding of our invention, reference may be had to the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims. Figs. 1 and 2 diagrammatically illustrate embodiments of our invention as applied to an electric translating system for transmitting a substantially constant direct current to a load circuit from a constant voltage alternating current supply circuit.

Referring now to Fig. 1 of the drawing, our invention is there diagrammatically illustrated as applied to an electric valve translating system for transmitting a direct current of constant value to a load circuit I from a constant voltage alternating current circuit 2. The load circuit i may be a welding circuit. As a means for obtaining a direct current of constant value, we may employ suitable apparatus, such as a monocyclic net work 3, an inductive network comprising a transformer 4 and electric valve means 5, 6 and I. The monocyclic network 3 comprises a plurality of branches of reactances of opposite sign, such as inductances 8 and capacitances 9. The transformer 4 may comprise a plurality of primary windings lflarranged in a diametric connection which is disclosed and broadly claimed in United States Letters Patent 2,126,604, granted August 9, 1938, upon an application of Burnice D. Bedlord, and which is assigned to the assignee of the present application. The transformer 4 may also comprise a plurality of secondary windings ll, I2 and I 3 which may be considered to constitute the principal or main sections of the transformer windings, and which are also provided with extended sections l4, l5 and I6. The windings l4-l6 may be in phase with windings Il-l3, respectively, or may be displaced in phase with respect thereto. The secondary windings are provided with terminal connections l1, I8 and I9, and tap connections 20, 2| and 22, respectively.

The electric valve means 5-! are preferably of the type comprising an ionizable medium, such as a gas or a vapor, and each includes an anode 23, a cathode 24 and an associated make-alive or immersion-ignitor control member 25. The control members 25 are of a material having a relatively high specific electrical resistivity with respcct to that of the associated cathode 24 and may be of boron-carbide or silicon-carbide, or other suitable material having the desired characteristics. The cathode 2 3 may be a solid such as cadmium, or may be a liquid, such as mercury.

By employing transformer windings having extended sections for energizing the immersion-ignitor control members 25, it is possible to obtain a wider range of control of the output voltage of the electric valves where it is desired to employ the excitation circuits which are connected to the anode circuit of the associated principal electric valve. When extensions are employed, it has been found that the principal or main valves may be rendered conductive at points relatively close to the zero value of the positive half cycle of applied anode-cathode voltage Without requiring the lapse of an undesired period of time.

We provide an improved excitation circuit which is energized in response to the voltage applied to the anode of the principal electric valve and which may be connected to the extended section of the transformer winding. More specifically, referring to Fig. l, we provide a plurality of excitation circuits 26, 2'rl and 23 associated with electric valves 54, respectively, and each of which comprises a control electric valve 29 preferably of the type employing an ionizable medium and having an anode 30, a cathode 3i and a control grid 32. The broad feature of effecting de-- cnergization of the immersion-ignitor control members 25 after the initiation of an arc discharge within the electric valve means, is disclosed and broadly claimed in a copending patent application, Serial No. 108,587, of E. F. W. Alexanderson, filed October 31, 1936, and which is assigned to the assignee of the present application. We connect in the anode-cathode circuit of each of the control electric valves 29 a suitable impedance element, such as a resistance 33, which is energized by suitable apparatus, described hereinafter, to render the control electric valves 29 non-conductive and hence to effect deenergiza tion of the control members 25 when are discharges are established within the associated principal or main electric valves. The control electric valves 29 may be rendered conductive in turn by suitable excitation circuits. In Fig. 1 the grids 32 are shown as being connected to be responsive to the voltages of the extended sec tions of the transformer windings or responsive to the voltage of the total associated section. The grids 32 are connected to the transformer winding through a suitable resistance 3% which functions also as a current limiting resistance.

As a means for properly energizing the resistance 33 to render control electric valves 29 nonconductive, we provide a plurality of inductive devices, such as magnetically saturable transformers 35, each having a primary winding 36 and a secondary winding 371. The voltage produced by the secondary winding M is of a peaked wave form, when the device is of the saturable type. If the inductive devices 35 are unsaturable, it will be understood that the wave form of the output voltage of the secondary windings 31! will be rectangular; that is, the output voltage will have the same Wave shape as the current transmitted by the primary windings 36. The transformers 35 may be designed so that the peak value of the secondary voltage need only be approximately equal to, or slightly greater than, the voltage produced by the extended portion of the transformer winding.

The operation of the embodiment of our in vention shown in Fig. 1 will be explained by considering the system when it is operating to transmit a substantially constant current to the load circuit l from the constant voltage alternating current circuit 2. The monocyclic network transforms the constant voltage alternating current to alternating current of constant value, and the transformer l and the electric valves transform the constant current alternating current to direct current of constant value.

It will be understood by those skilled in the art that the electric valves 5-? will conduct current in a predetermined order established by the phase rotation of the system, and that in the three phase system illustrated each electric valve will conduct current for 120 electrical degrees, the current being commutated or transferred to that electric valve which has the most positive anode voltage during a particular interval. Of course, this transfer will not take place until the are discharge path of that valve is rendered conductive by the proper energization of the control member 25.

Considering the excitation circuit 26 associated with the main electric valve 3, let it be assumed that electric valve 71' has conducted current for substantially 120 electrical degrees and that the voltage impressed on anode 23 of electric valve 5 is slightly more positive in potential than that of valve 7. Since grid 32 of control valve 29 in ex citation circuit 26 is connected to a point of positive potential relative to the cathode 3!, control valve 29 will be rendered conductive to transmit an impulse of unidirectional current to the control member 25 of electric valve 5, thereby ren dering the electric valve 5 conductive. When the electric valve 5 is rendered conductive, current is transferred from valve l to valve 5. Of course, as the current is transmitted to the anode-cathode circuit of the valve 5, primary winding 36 of transformer 35 is energized and there is induced in the secondary winding 3'l thereof a voltage thereby producing across the terminals of resistance 33 a negative voltage which renders control electric valve 23 non-conductive. In this manner, the excitation circuit is deenergized and the control member 25 is deenergized. If the transformer 35 is designed to be saturable, the wave form of the voltage produced across the terminals of the resistance will be peaked and the transformer is designed so that the magnitude of this voltage is sufficient to render ineffective the positive voltage introduced into the circuit by means of the extended portion [4 of the transformer secondary winding. By deenergizing the control member 25, as soon as the are discharge is established the duty imposed on the control member 25 is substantially reduced, thereby increasing the life of the electric valve means.

Fig. 2 diagrammatically illustrates a further modification of our invention. The elements shown in Fig. 2 correspond to those shown in Fig. 1 and have been assigned like reference numerals. In the arrangement of Fig. 2, the control grids 32 of control electric valves 29 are energized from a separate excitation circuit 38 comprising a transformer 39 having primary windings 40 and secondary windings 4!. A suitable source of negative unidirectional biasing potential, such as a battery 42, may be employed if desired. The excitation circuit 38 may be connected to any suitable source of alternating current correlated in phase and frequency with the anode-cathode voltage. In the arrangement shown in Fig. 2, the

III

excitation circuit 38 is connected to the alternating current circuit 2 through a suitable phase shifting device such as a rotary phase shifter 43. By the adjustment of the rotary phase shifter 43, the time at which the control electric valves 29 are rendered conductive may be independently adjustable. The excitation circuit 38 also serves to prevent conduction by the control electric valves 29 near the end of the periods of conduction by electric valves 5-1.

While we have shown and described our invention as applied to particular systems of connections and as embodying various devices diagrammatically shown, it will be obvious to those skilled in the art that changes and modifications may be made without departing from our invention, and we, therefore, aim in theappended claims to cover all such changes and modifications as fall within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a supply circuit, a load circircuit, electric translating apparatus connected between said circuits and including an inductive network having a winding and an electric valve means comprising an anode, a cathode and a control member, said winding having a terminal connection and a tap connection, means for connecting said anode to said tap connection, means for energizing said control member comprising a control electric valve having an anode, a

cathode and a grid, means for energizing said grid to render said control electric valve conductive and thereby to render said first men-' tioned electric valve conductive, and means connected between the anode-cathode circuits of said first mentioned valve and said control valve to render said control valve non-conductive upon the initiation of a discharge in said first mentioned valve.

2. In combination, a supply circuit, a load circuit, electric translating apparatus connected between said circuits and including an inductive network having a winding and an electric valve means comprising an anode, a cathode and a control member, said winding having a main section and an extended section, means for connecting said anode to said main section, means for energizing said control member comprising a control electric valve having an anode, a cathode and a grid, means for connecting the anodecathode circuit of said control valve to said extended section of said winding, means for energizing said grid to render said control valve conductive and thereby to render said first mentioned valve conductive, and means including a saturable inductive device connected between the anode-cathode circuits of said first mentioned valve and said control valve to render said control valve non-conductive upon the initiation of a discharge in said first mentioned electric valve.

3. In combination, a supply circuit, a load circuit, electric translating apparatus connected between said circuits and including an inductive network having a winding and an electric valve means comprising an anode, a cathode and a,

control member, said winding having a main section and an extended section, means for connecting said anode to said main section, means for energizing said control member comprising a control electric valve having an anode, a cathode and a grid, means for connecting the anodecathode circuit of said control valve to said extended section of said winding, means for energizing said grid to render said control valve conductive and thereby to render said first mentioned valve conductive, an impedance element connected in series relation with the anodeoathode circuit of said control electric valve, and an inductive device having a primary winding connected in series relation with the anodecathode circuit of said first mentioned valve and having a secondary winding connected across said impedance element to introduce into the anodecathode circuit of said control valve a negative voltage to render said control valve non-conductive upon the initiation of an arc discharge within said first mentioned valve.

4. In combination, a supply circuit, a load circuit, electric translating apparatus connected between said circuits and including an inductive network having a winding and an electric valve means comprising an anode, a cathode and a control member, said winding having a main section and an extended section, means for connecting said anode to said main section, means for energizing said control member from said extended section and comprising a control electric valve 'having an anode, a cathode and a grid, means for energizing said 'grid in response to the voltage of said extended section to render said control electric valve conductive and thereby to rendersaid first mentioned valve conductive, and a saturable inductive device connected in the anode-cathode circuits of said first mentioned valve and said control valve to efiect deenergization of said control member upon the initiation of an arc discharge within said first mentioned electric valve.

5. In combination, a supply circuit, a load circuit, electric translating apparatus connected between said circuits and including an inductive network having a winding and an electric valve means comprising an anode, a cathode and a control member, said winding having a main section and an extended section, means for connecting said anode to said main section, means for energizing said control member from said extended section and comprising a control electric valve having an anode, a cathode and a grid, means for energizing said grid in response to the voltage of said supply circuit to render said control valve conductive and thereby to efiect energization of said control member, and a voltage inductive device connected in the anode-cathode circuits of said first mentioned valve and said control valve to effect deenergization of said control member upon the initiation of an are discharge within said first mentioned electric valve. control valve to effect deenergization of said con- 6. In combination, a supply circuit, a load circuit, electric translating apparatus connected between said circuits and including an inductive network having a winding and an electric valve means comprising an anode, a cathode and a control member, means for connecting said anode to said winding, means for energizing said control member comprising a control electric valve having an anode, a cathode and a grid, means for energizing said grid to render said control electric valve conductive and thereby to render first mentioned electric valve conductive, and a saturable inductive device connected between the anode-cathode circuits of said first mentioned 1 valve and said control valve to render said control valve non-conductiveupon the initiation of a discharge in said first mentioned valve. I

BURNICE D; BEDFORD. ELMO E. MOYER. 

